A highly precise, quantitative computerized method of assessing phalangeal limb densities from scans of the X-ray film image will be used to follow the long term bone density changes of up to 75 three-to-six-year-old lead poisoning patients receiving chelation therapy to extract stored lead from bone. The radiological changes as indicators of stored lead will be correlated with concomitant clinical measures such as blood lead levels, free erythrocyte protoporphyrin, hematocrit and hemoglobin with a view toward making the radiological measures part of a battery of tests to distinguish chronic from acute poisoning. A new computer algorithm for assessing changes in bone has been developed which utilizes the same radiographs, but which ascertains radiological ash density instead of the current radiological limb density. This new mode will be tested against the current measure to see whether it actually demonstrates an expected increased sensitivity to bone changes. Correlations of the two radiological modes with the clinical methods will be carried out by multivariate analysis of variance and other statistical measures using hand/wrist radiographs of 400-600 children in the Columbus (Ohio) Lead Poisoning Prevention Program survey. These tests will require that we enlarge our phalangeal density data base to include more white and black control subjects in the age range three to six years and to establish ash weight and ash density norms. In addition, we expect to continue developing methods to portray the distribution of bone mineral along the bone axis so that localized regions of excess density can be pinpointed objectively without recourse to the usual subjective methods of visual scrutiny of radiographs.